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Re: Are LED light's circuit board shielded against strong EMF and RFI?

Originally Posted by PhotonWrangler

1) Find a portable AM radio.
2) Tune it to an empty spot at the low end of the band.
3) Turn on the flashlight and hold it up to the radio's antenna.

If you hear the flashlight's PWM circuit buzzing in your radio, EMF is getting out. And if EMF can get out, it can also get in.

Depending on frequency (wavelength). I'm not an EE so I can't tell you if low-frequency (long-wavelength) EMF is a problem, but a conductive shell with holes of a given size can block EMF over a certain frequency, that frequency being based on the hole size. Now, I have no idea if that matters or if I'm just being pedantic.

I am not able to really evaluate this source, but it seems coherent and discusses EMP testing:ECE.unm.edu

Apparently it's not really feasible to test with a nuke, which causes an EMP mainly by slamming gamma rays into the atmosphere, releasing electrons at high speed, generating a magnetic field very quickly, which pushes the Earth's field rapidly to cause damage to things. Instead we use electronics to generate an EMP, like a

In short:

EMP generation outside controlled tests are hard to predict and plan for. I see lots of people talking about testing this or that, but not much real data. Give these guys a call:

Re: Are LED light's circuit board shielded against strong EMF and RFI?

Guys,

Thank you all for the great inputs, the main reason I am asking this question is because some flashlight manufacturers advertise their lights as designed to "Mil-Spec", so I am assuming a piece of equipment designed and tested to military specifications generally speaking are shielded against some EMP and RFI no?

LED flashlights are great, great runtime and super bright but if a burst of EMP or RFI can potentially fried out the circuit board are they (LED) still the preferred choice? Quoting Murphy's law here, things that can fail will fail. Keeping things simple, any assault rifles can fail but not a bayonet.

Re: Are LED light's circuit board shielded against strong EMF and RFI?

More food for thought -

One point of ingress and egress for EMI/RFI is directly through the lens, which by definition is not made of metal. While a thin coating of a conductive material can be vapor-deposited onto the lens, this will only provide very weak protection against electromagnetic fields. Anything that has a lens is vulnerable because of the lens.

As an example, many years ago I was running a video camera at a live event on an outdoor stage. It just so happened that the event was being held a half mile away from a radio station's transmitter tower. While the camera's body was very well shielded and did a great job of deflecting RFI, any time I pointed the lens in the direction of the tower I got a screenful of hash. There was no way to shield the optics from the RFI.

Re: Are LED light's circuit board shielded against strong EMF and RFI?

Originally Posted by PhotonWrangler

More food for thought -

One point of ingress and egress for EMI/RFI is directly through the lens, which by definition is not made of metal. While a thin coating of a conductive material can be vapor-deposited onto the lens, this will only provide very weak protection against electromagnetic fields. Anything that has a lens is vulnerable because of the lens.

As an example, many years ago I was running a video camera at a live event on an outdoor stage. It just so happened that the event was being held a half mile away from a radio station's transmitter tower. While the camera's body was very well shielded and did a great job of deflecting RFI, any time I pointed the lens in the direction of the tower I got a screenful of hash. There was no way to shield the optics from the RFI.

Re: Are LED light's circuit board shielded against strong EMF and RFI?

Originally Posted by ganymede

Guys,

Thank you all for the great inputs, the main reason I am asking this question is because some flashlight manufacturers advertise their lights as designed to "Mil-Spec", so I am assuming a piece of equipment designed and tested to military specifications generally speaking are shielded against some EMP and RFI no?

LED flashlights are great, great runtime and super bright but if a burst of EMP or RFI can potentially fried out the circuit board are they (LED) still the preferred choice? Quoting Murphy's law here, things that can fail will fail. Keeping things simple, any assault rifles can fail but not a bayonet.

LOL , mil-spec , i can just imagine a "opposition" parked away from a base with a Df directional antenna with a receiver that tunes from 30khz to 400khz or so listening out for those on low power or moonlight mode using PWM .

Re: Are LED light's circuit board shielded against strong EMF and RFI?

Originally Posted by HooNz

LOL , mil-spec , i can just imagine a "opposition" parked away from a base with a Df directional antenna with a receiver that tunes from 30khz to 400khz or so listening out for those on low power or moonlight mode using PWM .

Positioning!

Interesting! Did we unknowingly gave our position away to our enemies?

Re: Are LED light's circuit board shielded against strong EMF and RFI?

If they're using Hall Effect sensors as that thread indicates, I would expect it to be activated by strong magnetic fields. On the one hand this is an interesting design and was probably done for reliability - get rid of the mechanical corrosion-prone metal contacts and perform the on/off switching with a solid state sensor. This will enable the switch to provide reliable service for a long, long time. On the other hand, they probably need to include some mu-metal shielding around the Hall effect sensor to prevent accidental activation from external magnetic stimuli.

Re: Are LED light's circuit board shielded against strong EMF and RFI?

Originally Posted by ganymede

Thank you all for the great inputs, the main reason I am asking this question is because some flashlight manufacturers advertise their lights as designed to "Mil-Spec", so I am assuming a piece of equipment designed and tested to military specifications generally speaking are shielded against some EMP and RFI no? . . . .

No. There are thousands of Military Specs - unless they say which part of which Military Spec it complies with, it's one of those brilliant Marketing strikes - makes the customer believe wonderful things about the product, and if challenged, they justify the statement by giving one trivial example of Spec compliance.

Re: Are LED light's circuit board shielded against strong EMF and RFI?

Originally Posted by PhotonWrangler

. . On the other hand, they probably need to include some mu-metal shielding around the Hall effect sensor to prevent accidental activation from external magnetic stimuli.

Exactly - the results show that there was inadequate field testing of the design - typical customers are having serious problems - a flashlight turning on and flattening the battery is a serious problem.

If the problem only happened close to an MRI machine, you could accept it, but not from fridge magnets or cars starting.

It doesn't have to be MuMetal - a piece of steel will provide provide serious magnetic field shielding.

Maybe just reducing the sensitivity - a small magnet so close to the sensor creates a huge Magnetic field.

Re: Are LED light's circuit board shielded against strong EMF and RFI?

Originally Posted by MikeAusC

No. There are thousands of Military Specs - unless they say which part of which Military Spec it complies with, it's one of those brilliant Marketing strikes - makes the customer believe wonderful things about the product, and if challenged, they justify the statement by giving one trivial example of Spec compliance.

Re: Are LED light's circuit board shielded against strong EMF and RFI?

You might be interested in:http://www.candlepowerforums.com/vb/...buse-by-1-what
I would have liked to leave it in the microwave longer but didn't want to risk blowing up thr oven.....they don't like operating without a load..
I still have that flashlight and it still works!

Re: Are LED light's circuit board shielded against strong EMF and RFI?

Originally Posted by 1 what

You might be interested in:http://www.candlepowerforums.com/vb/...buse-by-1-what
I would have liked to leave it in the microwave longer but didn't want to risk blowing up thr oven.....they don't like operating without a load..
I still have that flashlight and it still works!

Excellent videos! About the microwave oven operating without a load, you could stuff a flashlight into the turkey come next thanksgiving...

Re: Are LED light's circuit board shielded against strong EMF and RFI?

In response to the OP's question - there's a visible flickering in low mode of a current-regulated flashlight (Fenix LD01 R4) when it's placed few centimeters from a GSM cell phone during a text message transmission.

I'm not an expert on RF so I'm not sure if this is a normal occurence for a flashlight. So far I've witnessed only usual side effects of GSM transmission on PC loudspeakers and some CRT displays.